The origin of the runaway high-mass X-ray binary HD 153919/4U1700-37

Abstract

Based on its Hipparcos proper motion, we propose that the high-mass X-ray binary HD 153919/4U1700-37 originates in the OB association Sco OB1. At a distance of 1.9 kpc the space velocity of 4U1700-37 with respect to Sco OB1 is 75 km s^-1. This runaway velocity indicates that the progenitor of the compact X-ray source lost about 7 M_sun during the (assumed symmetric) supernova explosion. The system's kinematical age is about 2 +/- 0.5 million years which marks the date of the supernova explosion forming the compact object. The present age of Sco OB1 is la 8 Myr; its suggested core, NGC 6231, seems to be somewhat younger ( ~ 5 Myr). If HD 153919/4U1700-37 was born as a member of Sco OB1, this implies that the initially most massive star in the system terminated its evolution within la 6 million years, corresponding to an initial mass ga 30 M_sun. With these parameters the evolution of the binary system can be constrained. Based on data obtained with ESA's astrometric satellite Hipparcos.